The stock has been under pressure since last week, when Facebook reported its first earnings as a public company and failed to relieve investor worries about slowing sales growth and its plan for mobile advertising.

As Facebook’s stock continues to bleed, institutional investors are beginning to unload their stakes. Fidelity Investments, which owns both public and private shares of Facebook, sold more than 1.9 million public shares in June across 21 different mutual funds, according to Morningstar data.

The moves represent an about-face for Fidelity, one of the first institutional investors to take a significant stake in Facebook and the country’s third-largest mutual-fund company by assets. Fidelity’s funds owned the shares for at most six weeks — much shorter than the median holding period of about 22 months for U.S. stock funds, according to Morningstar.

“Fidelity managers are known to like to buy things in order to kick the tires and ask questions,” said John Bonnanzio, editor of Fidelity Insight, a newsletter that tracks the company’s funds and that provided the data on the funds’ private Facebook purchases. “It seems they ultimately decided that they don’t like what they see.”